If the S bit is set (RSBS), the N and Z flags are set according to the result, and the C and V flags are set as follows: C if the result generated a borrow (a not carry; unsigned underflow); V if the result generated a signed overflow.

Because operand 2 is able to be a register or immediate with shifting, you can do things such as negation (0 - Op1) or various types of fast multiplication.

There is also RSC to perform subtraction with the Carry flag considered.